A plot synopsis of Così Fan Tutte reads with about as much interest as a treatise on the love life of salt and pepper shakers. Two swains, Ferrando (Robert Mack) and Guglielmo (Marian Pop) convinced of the unshakeable fidelity of their fiancés, Dorabella (Elizabeth Stannard) and Fiordiligi (Caitlin Lynch), bet Don Alfonso (Kristopher Irmiter) that the young women can pass any test put to them. Don Alfonso, of course, disagrees. Under the pretense of being conscripted into battle, the young men depart, to reappear disguised as Albanians and court each other's fiancés. They are abetted in this by Despina (Sarah Callinan) the young women's maid, who at various points in the opera appears in disguise, too, as a mesmerist doctor – hypnosis was the rage in Europe during the time Cosi was written – and as a lawyer bearing marriage contracts at the end. Ferrando and Guglielmo initially appear to be proven right, but after a feigned suicide attempt – "cured" by the mesmeric doctor – and additional passionate courtship the resolve of first Dorabella and then of Fiordiligi give way, and indeed they nearly marry their Albanian suitors in a ceremony presided over by the disguised Despina. The conclusion, in which the Albanians disappear, to reappear as the perfectly furious Ferrando and Guglielmo, revealing the mechanics of the plot, is ironic, a philosophical shrug. In some productions the couples switch their paramours; it some they return to their original fiancés, as was the case in Mozart's day.

Cosi, which is the third opera Mozart wrote with Lorenzo da Ponte has always suffered in comparison with The Marriage of Figaro and Don Giovanni due to this schematic plot. Beethoven, who yearned for the kind of love which could storm dungeons, as in Fidelio, detested it. Bernard Shaw pronounced it twaddle. But both Richard Strauss and Gustav Mahler, the greatest composer-conductors at the turn of the century, adored Cosi, and a decisive case was made for it when Fritz Busch conducted and recorded it at one of the first Glynebourne festivals in the mid 1930s. Since then it has become a staple. The reason is simple: the story may be trite, but Mozart bathes these undertakings in musical element of the gods.

As a technical feat, it brings to mind "Love's Labour's Lost," the only play by Shakespeare written entirely in verse, whose atmosphere it shares. Cosi is facetted like a diamond with duets, trios, quartets, quintets, sextets which follow each other head on heel in a manner which is as lifelike as the best portraiture and yet is jarringly like a theorem. The solo arias of each lover cleverly parody the histrionic conventions of opera seria. Dorabella and Fiordiligi may be silly girls, but they see themselves as heroines from Racine, or the operas of Gluck. Both Ferrando and Guglielmo's arias also serve as proof that every fall guy sees himself as a hero. The Mozart biographer Maynard Solomon has pointed out that the courtship music illustrates how play-acted emotions can become real ones, which is Cosi’s subtle feat. The orchestral music is on the magnitude of the Jupiter symphony, its contemporary in Mozart's catalogue, and contains some of Mozart's most delicious writing for wind instruments. It is as sexy as the most libidinous paintings of Boucher. No other composer equals Mozart in showing in music the quickening beat of the heart when aroused.

James Meena, the conductor, is a real Mozartian, alert to Cosi’s many shifting moods. He knows when to let the music breathe and when to forge ahead, which is by no means obvious in a work of Cosi’s complex texture. The wind players, who almost mirror the protagonists throughout the score, were also in specially good form. The Don Alfonso, Kristopher Irmiter, who delighted last year as Figaro in Opera Carolina's The Marriage of Figaro, seems to have Mozart in his bones, which is why I wish he had performed his part of the great trio "Soave Si Il Vento" with more tendresse, and less irony. There is no reason at all in the music why the Don cannot also be touched, even while laughing up his sleeve. Robert Mack, who was indisposed, sang only segments of his role as Ferrando; the expedient of placing another tenor in the pit to sing for him was employed otherwise, so his performance cannot be evaluated, as it was sketched. One of the secret pleasures of regional opera is the untarnished beauty of the voices of the young-ish casts, and Marian Pop, the Guglielmo, as well as Elizabeth Stannard and Caitlin Lynch, the Dorabella and Fiordiligi respectively, all were a pleasure to hear. Stannard, whose voice is sumptuous, has not quite found the requisite vocal agility for Dorabella. Listening to her, I felt she is at heart a Wagnerian singer, and the coloratura element of Dorabella's role was alien to her. But Caitlin Lynch's Fiordiligi is already well on the way to becoming a mature and touching performance, as Sarah Callinan's Despina is a well-timed and witty one.

Opera Carolina's Cosi was set in the 1920's, the men dressed in Navy whites, the women dressed as flappers. The production went off kilter when the men returned as Albanian suitors, which were played as broad farce with the men dressed in costumes of ostentatious middle-eastern-ness. They resembled the imbecilic wise-men of Amahl and the Night Visitors more than anything else. It might have been far more pertinent to have them dressed as Rudolph Valentino as The Sheikh, which was a 1920s erotic idée fixe. From then on, things were played too broadly for Cosi’s ineffable qualities. Only Caitlin Lynch's Fiordiligi was able to transcend this. Cosi may be silly, but the music is for adults. This might have been an entirely splendid performance with a little more time and a little more sense. A little more wisdom in the costuming, less shtick in the direction. In the case of Mozart, it is seldom a mistake to err in the direction of subtlety.